This invention relates generally to instrumentation for pulmonary diagnosis, and more particularly pertains to a breath transducer functioning under the force of specimen breath to provide lineal displacement of its diaphragm for allowing diagnosis of the specimen's lungs and a possible detecting of early signs of pulmonary disorders.
Various types of pulmonary diagnostic instruments have long been available upon the market for use as a means for broadly testing for respiratory dysfunction of persons who are believed to be inflicted with some form of respiratory impairment. Instrumentation of this nature appears to be one expediency available to the medical profession as a means for detecting such disorders, since any such disease or obstruction somewhere within the remote confines of the lung are difficult of detection, do not provide any form of direct manifestation of existence, and do not lend themselves to any form of probe for direct analysis, and hence, such difficulty of detection originally led to the various forms of tests that could be conducted upon the respire of breath as a means for sensing an indication of what perhaps might be a lung disfunction.
Any analysis of lung disease, heretofore, in this manner, for those forms of disease which lead to chronic airway obstruction, is generally recognized by the profession as one of the most important and yet frustrating health problems in existence, with the treatment of such diseases being particularly frustrating because by the time the patient usually seeks medical assistance, such as due to the physical manifestation of his shortness of breath, or the like, or because some form of diagnostic test has finally revealed an abnormal pulmonary function, the disease is generally to that stage of development that it has become incurable. Part of this problem is due to the fact that present pulmonary diagnostic instruments are not sufficiently sensitive enough to provide an early warning of incipient diseases of the lung, but rather, such present instrumentation exhibit a rather wide variance of tolerance limits in their measurements that are really of very little assistance to the pracititioners in their attempts to practice preventative type medicine for at least an early curtailment of any beginning lung disease.
Reportedly, among the most useful of pulmonary examinations that is currently receiving some attention as a means for detecting potential or developing disease of the lungs is the measurement for closing volume of the lungs during functioning of one's respiratory system. Closing volume has generally been defined as a measurement which may perhaps detect respiratory disease in its preclinical stages. It is the lung volume during expiration over which emptying of the dependent regions of the lung is severly reduced or ceases all together. A certain amount of closing volume exists in most individuals, with the capacity for closing volume gradually increasing with age, a phenomenon that is thought to exist and occur due to the changes in the lung elastic recoil over a lifetime. Hence, certain standarized forms of information are available regarding closing volume, and which can and do establish the health parameters for individuals with normal pulmonary functioning. On the other hand, persons that have either definite lung disease, or those that subject themselves to excessive tobacco smoking, exhibit changes generally of detrimental form in the measurement of their closing volumes which may give a ready indication that airway obstruction is developing or has long developed, and perhaps is amplifying to dangerous levels, so that the physician knows that disease is present and a medical reality in the lungs.
Medical authors have expressed the opinion that existing pulmonary devices are not accurate enough to provide the type of information that is needed for diagnosis of early airway diseases, but state that if such tests could be conducted upon instrumentation that would function sensitive and precision enough, then perhaps lung related diseases could be detected at their much earlier stages of development and lead to much more effective if not preventative treatment. Hence, sensitive instrumentation would be useful to provide patient pulmonary analysis on a much more great scale, and could even be used as a screening program for testing whole masses of people, and through the utilization of such sensitive test results, and their comparison with known health parameters, provide the medical examiner with sufficient information for determining whether any one individual tested may possibly be developing incipient lung and airway disease. Hence, such sensitive tests, including closing volume, could probably detect early lung damage, and possibly at a stage when it is still totally reversible.
Various types of pulmonary devices are presently available upon the market, and generally operate under a variety of principles to achieve breath analysis for determining, particularly, the closing volume of the lung in addition to other pertinent information. Such devices, as previously analyzed, have been of questionable accuracy, but in any event, they generally incorporate various types of spirometric instrumentation for analyzing the air respiring from the lungs. Such tests, more specifically, may provide an analysis of the nitrogen washout, including closing volume, vital capacity, and other lung air flow volumes of breath, and the information obtained from these tests is useful for providing some basis for medical analysis of the patient. Such devices may include the Expirometer as presently marketed by the Warren E. Collins, Inc., of Braintree, Mass. The spirometer functions under the principle of rotating turbine blade means to reflect a light on a photo-transistor for producing pulses that are counted by digital logic for yielding a direct volume readout of pulmonary flow rate. The Spirostat is a turbinometer, having bi-directional measuring attibutes, and which measures the rotational speed of turpine like vanes which is proportional to the flow of the specimen breath. This device is manufactured and marketed by Fibre-O-Optics Industries, Inc., of West Palm Beach, Florida. Other forms of prior art pulmonary analyzing devices include the Pulmonary Functioning Indicator, as manufactured and sold by Chemetron Corporation, of Chicago, Illinois, and the Pulmonary Function Analyzer, as marketed by the Monaghan Company of Denver, Colorado. Both of these two latter devices incorporate a thermistor, either of the hot wire type or the trimetallic bead type, which when cooled by expired breath provides a read out of information relating to lung volume and breath flow.
The problems with many of these prior art spirometers is accurately described in the New England Journal of Medicine, Volume 289, No. 24, commencing on page 1283, and entitled "Evaluation of Electronic Spirometers," by FitzGerald, Smith, and Gaensler. For example, in a test using the Spirometer for determining maximum voluntary ventilation, the subject instrument underestimated this measurement on the average of 44 percent. The Pulmonary Function Analyzer underestimated by 21 percent the true measurement for maximum voluntary ventilation during the instrument evaluation. In their evaluation of these instruments for their effectiveness in measuring the forced vital capacity of the subjects being tested, the Pulmonary Function Indicator recorded volumes that were 20 to 50 percent high. The Spirostat recorded accurate volumes only at rapid flow rates, but that when its syringe emptying time exceeded two seconds, the volume was seriously overestimated. In the forced expiratory volume in one second test, the Pulmonary Function Indicator showed almost random scatter of measurements, with values deviating from the expected by as much as plus 40 percent to a minus 85 percent. In forced vital capacity tests, the Expirometer recorded readings as much as 16 percent over what the reading should have been, and it was determined that this occurs in the turbinometer type of instrument due to the inability of vane type meters to quickly change their velocity during uneven breath flow type tests.
Such deviations in measurements of pulmonary function provide information that certainly cannot be utilized by the practitioner with any confidence as a means for determining the presence of pulmonary disease, particularly at an early stage. As the authors state in the aforesaid article: "The increasing prevalence of chronic obstructive lung disease underlines the importance of screening of ventilatory function in the physician's office, in the clinic, and at the bedside." But that unless the present instruments " . . . are accurate and stable in the clinical context their general use may prove misleading in individual cases and eventually may discredit screening procedures of proved value." They summarize that the permissible range of deviation of plus or minus 5 percent from the primary standard is needed to observe the course of disease or the effect of drugs in an individual patient. "Electronic spirometers offer sufficient convenience advantages to justify further development. The instruments that we examined would not be recommended in their present form because of insufficient accuracy and because three lacked facilities for calibration. Furthermore, convenience advantages are offset by high cost and lack of permanent record without expensive accessory equipment."
One other instrument is presently and commonly used for measuring the velocity of respiratory air currents. This device is entitled the Pneumotachograph, and is sold by Instrumentation Associates of New York, N.Y. This device operates upon the principle of passing the breath through a plurality of small diameter ducts, being approximately 0.8 mm. in diameter and 32 mm. in length. And, the instrument then measures the pressure differential between the air entering the series of ducts, and that leaving said ducts, and the measurement of this pressure drop providing a reading as to the representative velocity of expired breath. One advantage of utilizing this type of a pressure drop or differential measurement is that it is much more responsive instantaneously to the exact quantity and velocity of the passing breath, but one draw back is that it is difficult to control the conversion of such measurements to representative values of breath flow so as to provide accuracy in read out, and this is due mainly because there is no physical manifestation of this pressure differential that can be easily detected and gauged by supporting mechanism. In addition, this prior art instrument is quite elaborate of structure, and expensive of cost.
Hence, in view of the foregoing, it can be stated effectiveness, accuracy, and reliability of diagnostic equipment is just as important to patient welfare as the effectiveness, precise dosage, and purity of administered drugs. The need for instrumentation to provide accurate pulmonary diagnosis is readily apparent from the measurements and testing that has been made upon existing prior art devices.
It is, therefore, the principal object of this invention to provide a pulmonary diagnostic instrument and its accompanying transdueer which operates upon the principle of lineal displacement of its partial diaphragm to provide accurate measurements representative of information that may provide a determination of the closing volume of a specimen, in addition to other forms of related types of preliminary measurements.
It is another object to provide a pulmonary diagnostic instrument which is sufficiently sensitive to provide precise measurements regarding lung operation, and for furnishing more definite information for the physician to make early detection of potential and beginning lung disease.
It is a further object of this invention to provide a pulmonary instrument including a breath transducer that achieves a reproducible line or lineal displacement of its suspended diaphragm in direct relation to the force of movement, or flow rate, of the specimen breath therethrough, with the displacement being detected, gauged, and correlated to provide direct readout of information for lung analysis.
It is an additional object of this invention to provide a breath transducer for a pulmonary diagnostic instrument that functions to provide very sensitive and accurate information pertaining to the closing volume of a patient being screened.
Another significant object of this invention is the provision of a breath transducer for a diagnostic instrument which is replaceable and disposable.
A further object of this invention is to provide a mouthpiece transducer for a diagnostic instrument which can be quickly and promptly inserted or removed from its holder to facilitate its prompt usage and disposal.
Another object of this invention is to provide a breath transducer incorporating a lineal displacement suspension diaphragm which maintains a standard of tolerance consistently within, or less than, a plus or minus 5 percent from the normal.
An additional object of this invention is the provision of a breath transducer that is disposable and thereby eliminates the possibility of communication of disease from one patient to another.
A further object of this invention is to provide a breath transducer for a diagnostic instrument that can be used for measuring and performing the standard closing volume tests, in addition to other forms of pulmonary tests generally administered by physicians, such as the nitrogen wash-out measurement.
Another object of this invention is to provide a breath transducer, and its associated diagnostic instrument holder, which are facile of manufacture, inexpensive in cost, and which lend themselves to assembly line manufacture.